Apoptosis & Necrosis Flashcards
What is apoptosis?
Programmed cell death
How does apoptosis work?
-prevents cells with accumulated genetic damage from dividing & producing cells which might develop into cancer cells
-p53 protein detects DNA damage -> apoptosis occurs if DNA damage is detected
-cell triggers series of proteins - release of enzymes (caspases) -> autodigest cell
-caspases - cascade of activated enzymes
Examples of apoptosis in health
-development - removal of cells during development, eg. interdigital webs
-cell turnover - removal of cells during normal cell turnover, eg. cells in the intestinal villi at the tips, to be replaced by cells from below
Examples of apoptosis in disease
Cancer
HIV
Apoptosis in cancer
-lack of apoptosis
-increase in tumour size & genetic mutations
-mutated p53 gene producing faulty p53 protein
-p53 protein can no longer detect DNA damage & instigate apoptosis
Apoptosis in HIV
-too much apoptosis
-HIV can induce apoptosis in CD4 helper cells
-number of antibodies in blood decrease
-immunodeficient state
What can trigger apoptosis?
DNA damage - single-strand break, base alteration, cross-linkage
What is necrosis?
-death of most or all of the cells in an organ or tissue
-due to disease, injury or failure of the blood supply (an external factor)
What are clinical examples of necrosis?
-toxic spider venom
-frostbite
-infarction due to loss of blood supply, eg. cerebral infarction
-avascular necrosis of bone, eg. femur has single arterial supply through the neck of the femoral head
-pancreatitis
What happens after necrosis?
-body clears up the mess
-macrophages phagocytose dead cells
-necrotic tissue often replaced by fibrous scar tissue (unless the tissue can regenerate)
Caseous necrosis
-soft-cheese like appearance of tissue
-could be TB
-order stains for mycobacteria
